Abstract: Boron and fluorine codoped TiO_2 powders were prepared by hydrolysis of titanium tetra-n-butyl oxide in a mixed NH_4F-H_3BO_3-H_2O solution. The XRD results showed that the co-doping of boron and fluorine could not only efficiently inhibit the grain growth but also suppress the phase transition of anatase to rutile. When the molar ratios of B and F to Ti are 20∶ 100 and 5∶ 100 and calcined at 600 ℃, UV-vis spectroscopy of the sample showed better visible light responding. XPS results revealed that the Ti-B bonds and Ti-F bonds have formed which could extend the absorption spectra to visible light region and enhance visible light photocatalytic activity. When the molar ratios of B and F to Ti are 20∶ 100 and 5∶ 100 and calcined at 600 ℃, the degradation rate of 4-chlorophenol (4-CP) over the sample was about 1.5 to 3.0 times higher than that for other doped samples and undoped TiO_2. The total organic carbon (TOC) removal rates of 4-CP showed that 4-CP has been mineralized efficiently with the sample under visible light illumination.

Key words: co-doping;visible light;photocatalysis;band gap;TiO_2